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我对 python 编码比较陌生，我正在使用以下代码生成一个具有 40 个节点的图形，节点的布局是使用以下代码给出的：

 pos = nx.circular_layout(graph_anchor, **kwargs)

以下代码创建 graph_anchor：

    graph_anchor = convert_ebunch_to_graph(ebunch_anchor)

def convert_ebunch_to_graph(ebunch):
    g = nx.DiGraph()
    g.add_weighted_edges_from(ebunch)

我的问题是，我如何计算出节点的绘制顺序，即我如何计算出这段代码如何决定将哪些节点放在一起以及以什么顺序排列它们？

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1 回答 1

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From the source of nx.circular_layout:

def circular_layout(G, dim=2, scale=1, center=None):
    # dim=2 only
    """Position nodes on a circle.

    Parameters
    ----------
    G : NetworkX graph or list of nodes

    dim : int
       Dimension of layout, currently only dim=2 is supported

    scale : float
        Scale factor for positions

    center : array-like or None
       Coordinate pair around which to center the layout.

    Returns
    -------
    dict :
       A dictionary of positions keyed by node

    Examples
    --------
    >>> G=nx.path_graph(4)
    >>> pos=nx.circular_layout(G)

    Notes
    ------
    This algorithm currently only works in two dimensions and does not
    try to minimize edge crossings.

    """
    import numpy as np

    G, center = process_params(G, center, dim)

    if len(G) == 0:
        pos = {}
    elif len(G) == 1:
        pos = {G.nodes()[0]: center}
    else:
        # Discard the extra angle since it matches 0 radians.
        theta = np.linspace(0, 1, len(G) + 1)[:-1] * 2 * np.pi
        theta = theta.astype(np.float32)
        pos = np.column_stack([np.cos(theta), np.sin(theta)])
        pos = _rescale_layout(pos, scale=scale) + center
        pos = dict(zip(G, pos))

    return pos

It seems that positions are generated by dividing 360 degrees by the number of nodes. which node ends up where is decided by this line:

        pos = dict(zip(G, pos))

zip(G, pos) iterates through the nodes of the graph in order. and assigns positions to them. If you want to change the position, you need to change the order.

Example:

# make dummy graph
G = nx.from_numpy_array(np.random.rand(12,12)>0.5)

# test order of nodes:
for node in G.nodes:
    print(node)

0
1
2
3
4
5
6
7
8
9
10
11

pos = nx.circular_layout(G)
nx.draw_networkx(G, pos=pos)

enter image description here

Here, the first position that is assigned is that of node 0, then we go counterclockwise.

I could not find an easy way to change the order of the nodes in G, so here is a little workaround which creates a new graph with randomised order:

nodes = list(G.nodes(data=True))
edges = list(G.edges(data=True))
np.random.shuffle(nodes)

H=nx.Graph()
H.add_nodes_from(nodes)
H.add_edges_from(edges)

pos = nx.circular_layout(H)
nx.draw_networkx(H, pos=pos)

enter image description here

So changing the order of the nodes inside the graph changes where they will end up in the circular layout.

于 2020-06-14T13:21:34.297 回答